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Journal of Palaeogeography (20953836) 14(2)pp. 535-558
The investigation mainly focuses on larger benthic foraminifera, Canalispina, Siderolites, Loftusia, and Omphalocyclus from the Maastrichtian deposits (Tarbur Formation) in the Zagros Foreland Basin. The four new species: Canalispina zagrosia sp. nov., Siderolites persica sp. nov., Loftusia tarburica sp. nov., and Omphalocyclus tarburensis sp. nov., and four other index species: Siderolites calcitrapoides, Omphalocyclus cideensis, O. macroporus, and Loftusia baykali were identified. L. harrisoni is thought to be ancestor of L. minor, L. arabica, L. matsumarui, L. tarburica sp. nov., L. occidentalis, L. coxi, L. baykali, L. kahtaensis and L. oktayi during the early, middle and late Maastrichtian, while L. persica and L. elongata evolved into L. arabica in the middle Maastrichtian. L. turcica and L. morgani are close forms of L. elongata in the middle and late Maastrichtian, and L. anatolica and L. morgani are the predominant forms in the late Maastrichtian. The wall structures of Loftusia species are more complex in the late Maastrichtian than in early Maastrichtian forms due to evolutionary trends. Loftusia species with numerous whorls were predominant in the middle Maastrichtian. In contrast to this, the species with low whorl numbers during the early and late Maastrichtian were dominant. Detailed studies on Omphalocyclus species indicate that (1) the genus Omphalocyclus migrated from the middle part of the Tethys to other Tethyan areas during the late Campanian, and (2) the diversity of Omphalocyclus species of eastern Tethys (North African part) was higher than in other areas. © 2025 The Author(s)
Journal of Earth Science (1867111X) 35(5)pp. 1527-1545
A sedimentological investigation was carried out to reconstruct the paleogeography of the Zagros Foreland Basin. Based on the study of more than 1 000 rock samples, nine carbonate microfacies and three terrigenous facies were identified. The study reveals that the Maastrichtian succession was deposited in a widespread homoclinal ramp in the High Zagros Basin. Three (Gandom Kar area), two (Ardal area), seven (Gardbishe area), five (Shirmard area), two (Kuh-e-Kamaneh area), three (Kuh-e-Balghar area), and six (Murak area) of depositional sequences (3rd order) were identified. The thickness of the lowstand systems tract (LST) due to activities of local faults and subsidence in the southeast is more than in the central and northwest of the High Zagros Basin during the Early and Early Middle Maastrichtian. During the Middle Maastrichtian, the shallow and deep marine deposits were formed during the transgressive systems tract (TST) and highstand systems tract (HST) in this basin and the rate of subsidence in the center of this basin (Gardbishe area) is higher than in other areas and the platform was drowned in this area. The falling relative sea-level due to activities of local faults led to that marine deposits were absent in all parts of the High Zagros Basin (except the south part) during the Late Maastrichtian. Paleogeographical studies on the Zagros Basin during the Late Campanian–Maastrichtian showed the following results: shallow marine environments were developed in the south-east of this basin, and the turbidite, delta, and fluvial environments in the northwest were developed more than in other areas. © China University of Geosciences (Wuhan) and Springer-Verlag GmbH Germany, Part of Springer Nature 2024.
Schlagintweit, F. ,
Omidvar, M. ,
Safari, A. ,
Yazdi-moghadam, M. ,
Rashidi, K. Rivista Italiana di Paleontologia e Stratigrafia (20394942) 130(3)pp. 487-506
New data (onshore, offshore) on the Upper Cretaceous Ilam Formation of southwestern Iran are provided concerning the common presence of dasycladalean green algae (families Triploporellaceae, Polyphysaceae) that have so far been treated mostly in open nomenclature. The assemblage consists of the five taxa Salpingoporella ubaiydhi Radoičić, 1979, Dissocladella ondulata (Raineri, 1922), Trinocladus tripolitanus Raineri, 1922, Clypeina cf. dusanbrstinai Radoičić, 1997, and gen. et sp. indet. The taxa typically prevail in wackestones-packstones but exhibit different distributional patterns. While S. ubaiydhi and T. tripolitanus, rarely associated with D. ondulata, form a characteristic assemblage in a distal infralittoral facies (more diverse assemblage; zone no. 31 of Wynd, 1965), C. cf. dusanbrstinai occurs in a proximal infralittoral facies associated with miliolids among also complex forms (rhapydioninids) (assemblage zone no. 30 of Wynd, 1965). It is concluded that the two assemblage zones refer to different palaeoenvironments, instead of different ages (‘lower’ and ‘upper’). Based on benthic foraminifera, the main part of the Ilam Formation can be ascribed to the Santonian. For the lower part, a late Coniacian age is suggested implied indirectly by the comparably long vertical range of the rotaliid Orbitokathina vonderschmitti Hottinger, 1966 of the studied core. This would be in conformity with the K 150 Arabian Plate K 150 sequence boundary referring to a late Turonian?–early Coniacian hiatus. From a palaeobiogeographic perspective, T. tripolitanus is a cosmopolitan species, S. ubaiydhi is restricted to the area of the former Arabian Plate (subsurface Iraq, Saudi Arabia and Egypt), while C. dusanbrstinai has been recorded only from Serbia (type-locality). In addition to the algae, the stratigraphic discussion includes the occurrence of the benthic foraminifera Reticulinella? kaeveri Cherchi, Radoičić & Schroeder, 1989 and Orbitoides mid-orientalis (Eames & Smout, 1956) in the Ilam Formation. © 2024 Universita degli Studi di Milano. All rights reserved.
Annales Societatis Geologorum Poloniae (02089068) 94(1)pp. 61-82
This research attempted to determine the depositional sequences of the Qom Formation in the Urumieh-Dokhtar arc (Ghamsar section) and Esfahan-Sirjan fore-arc (Abadeh section) sub-basins in Iran, using microfacies and microtaphofacies analyses. The authors also investigated connections between the Qom Basin and the Zagros and Paratethys basins during the Oligocene. In this regard a total of eight microfacies, two terrigenous facies, and five microtaphofacies were identified on the basis of 269 samples from the Ghamsar section and 93 samples from the Abadeh section. The studied microfacies, terrigenous facies, and microtaphofacies were deposited on a homoclinal carbonate ramp. This carbonate platform can be divided into inner, middle and outer ramp environments. On the basis of the distribution of microfacies and sequence stratigraphy studies, five third-order depositional sequences and one incomplete depositional sequence were identified in the Ghamsar section and three third-order depositional sequences in the Abadeh section. According to the distribution of microtaphofacies and palaeobathymetric studies based on Amphistegina, the energy, and depth of the Qom sea in the Ghamsar section were greater than those evidenced in the Abadeh section. The results of local fault activity in the different sub-basins of the studied sections indicate a lesser effect of global sea-level changes in the Paratethys basin. On the basis of the formation of depositional sequences in these sub-basins; and differences in the number of depositional sequences; intense local fault activity is indicated during the Chattian Age (especially in the Urumieh-Dokhtar arc sub-basin). Regional sea-level fluctuations of the south Tethyan Seaway and the Paratethys Basin controlled sea-level changes in the Chattian Age. The depositional basins of the Tethyan seaway (southern Tethyan seaway, Paratethys Basin and Qom Basin) probably were related during the Burdigalian to Langhian and the early Serravallian. The results show that, the effect of sea-level changes of the Zagros Sea on the formation of depositional sequences in the Esfahan-Sirjan fore-arc sub-basin was significant. © 2024, Polish Geological Society. All rights reserved.
Journal of African Earth Sciences (1464343X) 202
The main purpose of this research main is to study the role of local faults in the formation of rudist assemblage composition and thickness in the Maastrichtian deposits of the Tarbur Formation in the High Zagros sub-basin. Based on the taphonomic studies and micro-biofacies analysis, three micro-biofacies were identified in the study areas. These micro-biofacies were formed in the shallow marine environments in the study areas. The Tarbur Formation in the Ardal and Murak areas was deposited in a high-energy environment based on the distribution of micro-biofacies. Other areas were formed in low-energy environments. The activities of local faults were an important and effective factor in the formation of rudist association with high thickness and the distribution of hydrodynamic energy in different areas of the carbonate platforms. The thickness of these rudist colonies increased from northwest to southeast in the High Zagros zone. © 2023 Elsevier Ltd
Acta Geologica Sinica (English Edition) (17556724) 96(1)pp. 147-166
Shallow carbonate deposits (Tarbur Formation) were formed in the Zagros foreland basin with dynamic tectonics during the Maastrichtian age. From the viewpoint of reconstruction of depositional conditions in these deposits, studies of biostratigraphy, microfacies, microtaphofacies, and sequence stratigraphy were performed in a single area at Tang-e Shabi Khoon, northwest of Zagros. Based on the identification of two assemblage zones consisting of benthic foraminifera in these strata, the formation was deposited during the middle to late Maastrichtian. The number of cycles in test size and type of coiling in Loftusia decreased from the study area toward the northwest of the Neotethys basin. The input of clastic sediments affected the distribution of Loftusia and rudists in the study area. Nine microfacies, six microtaphofacies, and one terrigenous facies (shale) were identified based on the sedimentary features. These deposits of the middle-late Maastrichtian were deposited on a homoclinal carbonate ramp. The platform can be divided into restricted and semi-restricted lagoon, shoal, and open marine environments. In the study area, the deposits of the Tarbur Formation were deposited during four third-order depositional sequences. Local fault activities affected the formation of depositional sequences in the study area. © 2021 Geological Society of China
Safari, A. ,
Ghanbarloo, H. ,
Purnajjari, S.M. ,
Moghaddam, H.V. Paleontological Research (13428144) 25(2)pp. 63-78
The Qom Formation deposits, located at 12 km southeast of Salafchegan (N: 34° 21′ 26″ and E: 50° 32′ 14″), have a thickness of 110 m. The formation includes thin, and medium-To-Thick bedded limestone, as well as shale, overlying the Lower Red Formation (early Oligocene) above an erosional unconformity. Its upper boundary is covered by alluvium sediments. Biostratigraphic distributions of benthic Foraminifera were used to determine the age and paleoenvironmental conditions of the Qom Formation. Two assemblage zones were recognized. Assemblage zones 1 and 2 were indicative of a Rupelian-Chattian age. The inner shelf (restricted and semi-restricted lagoons) and middle shelf (open marine) settings were formed on an open shelf platform. Euphotic conditions were dominant during the early and late Rupelian in the studied area. During the middle Rupelian, photic conditions were variable between euphotic and mesophotic to oligophotic. During the early and middle Chattian, photic conditions varied between oligophotic, mesophotic to oligophotic, and euphotic. During the late Chattian, mesophotic-oligophotic conditions were dominant. Additionally, a high level of salinity (40-50 and > 50 psu) was present in the studied area during the early Rupelian. The level of salinity varied from normal (30-40 psu) to hypersaline (40-50 psu) during the late Rupelian. Salinity during early and late Chattian subages was normal (30-40 psu). However, hypersaline (40-50 and > 50 psu) and normal (30-40 psu) conditions were present in the middle Chattian. Eutrophic to mesotrophic-oligotrophic conditions were found in the early Rupelian age. However, mesotrophy-oligotrophy dominated during the middle and late Rupelian and Chattian ages. In addition, the paleo-water depth of the Qom Sea fluctuated from < 10 m to > 20 m. Foralgal and foramol associations are dominant in the studied area during the Rupelian-Chattian ages. The general depositional environment of the Qom Formation is associated with seagrass meadows. © 2021 Palaeontological Society of Japan. All rights reserved.
Marine Micropaleontology (03778398) 162
This study examines the morphological changes of the Loftusia genus from the Zagros Belt of southern Iran using quantitative data. Eight Tarbur Formation outcrops were investigated in the High Zagros and the Lurestan sub zones. The observed Loftusia species are of mid Maastrichtian age in the High Zagros and the mid to late Maastrichtian age in the Lurestan and Murak areas, and they are often observed in deposits of the lagoon environments with high nutrient conditions. Two (Tang-e Shabi Khoon area) and four (Murak area) cycles were recognized based on the morphological parameter changes of Loftusia species. The correlation of the number of cycles of Loftusia species between the Zagros basin and the different areas of the Neotethys basin indicates that Loftusia species sizes change in time. The obtained data shows that the number of the sedimentary cycles (alternating shale and limestone layers) in the High Zagros zone is more different than the Lurestan zone. The High Zagros zone comprises rich terrigenous shale with higher nutrient flux in comparision to the Lurestan zone and other areas of the Neotethys basins. The number of cycles decreased from the southeast toward the northwest of the Neotethys basin. It is thought changes in Loftusia species in the Zagros basin are related to nutrient input during the Maastrichtian age and were independent of evolutionary trends. The genus Loftusia disappeared in the High Zagros zone at the end of the late Maastrichtian. The subsidence of the basin is associated with the Dena and High Zagros Faults. Due to the activities of those faults, the Tabur Formation was not deposited in the High Zagros zone areas. The genus Loftusia appeared in the southeast region of the Arabian plate during the early Maastrichtian, and migrated to the northwest of the Neotethys during the Maastrichtian. © 2020 Elsevier B.V.
Zeitschrift der Deutschen Gesellschaft fur Geowissenschaften (18601804) 171(4)pp. 503-519
One outcrop of the Qom Formation was measured for age determination and interpretation of palaeoenvironmen-tal conditions based on benthic foraminifera and the vertical distribution of microfacies and microtaphofacies in the Bijegan area of Iran. The study area is located about 20 km northeast of Delijan. There the Qom Formation is 162 m thick and dominantly contains thin, medium, thick bedded, and massive limestone. The formation overlies the Lower Red Formation in the Bijegan area. The upper boundary of the Qom Formation is formed by unconformably overlying recent alluvial sedi-ments. Three assemblage zones were identified. Assemblage zone 1 indicates a Rupelian age while assemblage zones 2 and 3 were deposited during the Chattian. The correlation between the curve of seawater depth changes and the distribution curve of microtaphofacies in the study area is indicative of a high energy environment (under the effect of the fair-weather wave base [FWWB] or storm wave base [SWB]) throughout the Rupelian-Chattian. Salinities are interpreted to have oscil-lated between normal marine (30–40 psu) and hypersaline (>50 psu) during deposition. The trophic conditions were mainly mesotrophic to oligotrophic. Euphotic conditions prevailed during the Rupelian and Chattian. In the Bijegan area, the Qom Formation formed in euphotic to meso-oligophotic conditions. Lagoonal and open marine environments characterise the lower section of the studied sequence (Rupelian and lower Chattian stages) and open marine conditions were dominant in the upper section of the study sequence (upper Chattian stage). Correlation of the study area with five other Rupelian-Chattian outcrops shows high sedimentation rate in the Qohrud area during the Rupelian and in the Mashhad Ardehal area during the Chattian. Throughout the Oligocene, the activity of local faults presumably affected sedimentation rates, sedimentary environments, and sea-level change in the Qohrud, Vidoje, Naragh, Bijegan, Mashhad Ardehal and Neizar areas. © 2020 E. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart, Germany.
Micropaleontology (00262803) 66(5)pp. 419-423
The large-sized agglutinated benthic foraminifera Loftusia Brady is a typical constituent of the shallow-water carbonates of the (upper) Maastrichtian Tarbur Formation, SW Iran (Zagros Zone). Different bio- and lithoclasts from the ambient depositional environment can be observed incorporated into the wall and other skeletal elements. These can include various small-sized benthic foraminifera belonging to different groups, but very rarely have planktonic forms have been observed inside the tests. The inclusion of a single specimen of an “Eocene planktonic foraminifera” observed within one of the type-specimens of Loftusia persica Brady (the type species of Loftusia) from Iran was reported in a recent paper by BouDagher-Fadel and Price (2009). The authors concluded that Loftusia persica represents an Eocene Lazarus taxon. Our conclusion (supported by abundant specimens from the Tarbur Formation of Iran) is that this single specimen is undiagnostic. Instead, Loftusia persica and the genus Loftusia are considered as Maastrichtian marker taxa that became finally extinct at the end Cretaceous. © 2020 Micropaleontology Press. All rights reserved.
Safari, A. ,
Ghanbarloo, H. ,
Mansoury, P. ,
Esfahani, M.M. Geologos (14268981) 26(2)pp. 93-111
During the Rupelian-Chattian, the Qom Basin (northern seaway basin) was located between the Paratethys in the north and the southern Tethyan seaway in the south. The Oligocene deposits (Qom Formation) in the Qom Basin have been interpreted for a reconstruction of environmental conditions during deposition, as well as of the influence of local fault activities and global sea level changes expressed within the basin. We have also investigated connections between the Qom Basin and adjacent basins. Seven microfacies types have been distinguished in the former. These microfacies formed within three major depositional environments, i.e., restricted lagoon, open lagoon and open marine. Strata of the Qom Formation are suggested to have been formed in an open-shelf system. In addition, the deepening and shallowing patterns noted within the microfacies suggest the presence of three third-order sequences in the Bijegan area and two third-order depositional sequences and an incomplete depositional sequence in the Naragh area. Our analysis suggests that, during the Rupelian and Chattian stages, the depositional sequences of the Qom Basin were influenced primarily by local tectonics, while global sea level changes had a greater impact on the southern Tethyan seaway and Paratethys basins. The depositional basins of the Tethyan seaway (southern Tethyan seaway, Paratethys Basin and Qom Basin) were probably related during the Burdigalian to Langhian and early Serravallian. © 2020 Sciendo. All rights reserved.
Safari, A. ,
Ghanbarloo, H. ,
Kasiri, A. ,
Purnajjari, S.M. Carbonates and Evaporites (08912556) 35(4)
Oligocene deposits of the Qom Formation in central Iran were studied to reconstruct the sedimentary environment and depositional sequences based on microfacies (MF) and micro-taphofacies (MTF) analysis. A total of 310 thin sections (210 and 100 from Vidoje and Neizar respectively) were studied to differentiate eight microfacies (MF) and five microtaphofacies (MTF) types. These MFs are representative of a variety of depositional environments including restricted and semi-restricted lagoons as well as open marine settings. Overall, the distribution of MFs at the two sites suggests an open-shelf setting for the Qom Formation. Three complete third-order depositional sequences together with one incomplete sequence were identified. In the Rupelian stage, sea level changes in the Neizar and Vidoje areas were most likely affected by tectonics controlled by regional faults, whereas regional sea-level fluctuations of the south Tethyan Seaway and the Paratethys Basin controlled sea-level changes in the Chattian stage. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.
Russian Geology and Geophysics (10687971) 60(12)pp. 1368-1384
This research attempted to reconstruct the sedimentary environment and depositional sequences of the Qom Formation in Central Iran, using biofacies and taphofacies analyses. The Qom Formation in the Andabad area (3º48'12.6″ N, 47º59'28″ E) is 220 m in thickness. The thickness of the Qom Formation in the Nowbaran area (35º05'22.5″ N, 49º41'00″ E) was found to be 458 m. In both areas, the formation consists mainly of shale and limestone. The lower boundary between the Qom and Lower Red Formations is unconformable in both areas. In the Nowbaran area, the Qom Formation is covered by recent alluvial sediments. In the Andabad area, the Qom Formation is unconformably overlain by the Upper Red Formation. A total of 122 limestone and 15 shale rock samples were collected from the Andabad area, and 94 limestone and 24 shale rock samples were collected from the Nowbaran area. Analysis of the collected samples resulted in the recognition of nine biofacies, one terrigenous facies, and five taphofacies within the Qom Formation in both areas. Based on the vertical distributions of biofacies, the Qom Formation is deposited on an open shelf carbonate platform. This carbonate platform can be divided into three subenvironments: inner shelf (restricted and semirestricted lagoon), middle shelf, and outer shelf. Two third-order and one incomplete depositional sequences were identified in the Nowbaran area, but in the Andabad area, three third-order and one incomplete depositional sequences were distinguished. © 2019, V.S. Sobolev IGM, Siberian Branch of the RAS.
Carbonates and Evaporites (08912556) 34(4)pp. 1293-1306
Qom Formation (Oligo-Miocene marine deposits of Middle Iran) in the southwestern Kashan was studied to determine its microfacies and depositional environments. Outcrops of the Qom Formation in the study area with 410 m, consist mainly of limestone, sandy limestone, shale and marl. Study section is unconformably underlain by the Eocene volcanic rocks and overlain by alluvium. Biogenic components of the Qom Formation comprise mainly of larger benthic foraminifera, coralline red algae and corals. Based on the presence of Nummulites spp. (Nummulites fichteli, Nummulites vascus, Nummulites cf. vascus, Nummulites sp.) throughout the study section, the Qom Formation is considered to be Rupelian in age. Microfacies analysis and field investigations on the study section led to recognition of six carbonate microfacies and two marl and shale facies. Two major depositional environments were identified in the study area including lagoon and open marine. Based on the recognized microfacies and field investigations, deposition of the Qom Formation in Barzok area took place on a carbonate ramp; besides, most of the carbonate parts of the study section are deposited in the open-marine settings. The high abundance of larger benthic foraminifera, coralline red algae and corals indicates that deposition took place in the tropical warm waters. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.
Journal of African Earth Sciences (1464343X) 140pp. 94-113
The Upper Cretaceous sediments in the Moghan area, NW Iran, contain diverse planktonic and benthic foraminifera, with a total of 33 genera and 53 species (17 genera and 38 species of planktonic foraminifera and 16 genera and 15 species from benthic foraminifera), which led to the identification of six biozones spanning the middle Campanian to late Maastrichtian. A detailed paleontological study and biostratigraphic zonation of these sequences has been carried out in four surface sections. This study shows that there are two different facies in the Moghan area, based on the faunal content. A deep open marine condition exists in the Molok, Selenchai and Nasirkandi sections. In these sections, Upper Cretaceous sequences have diverse planktonic foraminiferal species including the Globotruncana ventricosa (middle to late Campanian), Globotruncanella havanensis (late Campanian), Globotruncana aegyptiaca (latest Campanian), Gansserina gansseri (latest Campanian to early Maastrichtian), Contusotruncana contusa- Racemiguembelina fructicosa (early to late Maastrichtian) and Abathomphalus mayaroensis (late Maastrichtian) zones. This deep open marine setting grades laterally into shallower marine condition dominated by large benthic foraminifera such as Orbitoides media, Orbitoides gruenbachensis, Orbitoides cf. apiculata, Lepidorbitoides minor, Pseudosiderolites sp., Siderolites praecalcitrapoides, Siderolites aff. calcitrapoides and Siderolites calcitrapoides. This facies is mainly recorded in the Hovay section. A detailed biostratigraphic zonation scheme is presented for the studied sections and correlated with the results of other studies in the Tethyan realm. This is the first biozonation scheme for Upper Cretaceous sequences of the Moghan area that can be used as a basis for ongoing studies in this area and other parts of Tethys basin. © 2018 Elsevier Ltd
Neues Jahrbuch fur Geologie und Palaontologie - Abhandlungen (00777749) 287(2)pp. 123-142
Tubes of the characteristic serpulid species Rotularía spirulaea (Lamarck, 1818) are widespread in the Eocene of the Neo-Tethyan Realm. Here they are described from the state of Iran for the first time. Their ultrastructure and the mode of life, paleogeography and palaeoecology of this species are discussed. Rotularia spirulaea occurs in Eocene limestones of the Zefreh area. It is the most abundant member of a fossil association including Nummulites, bivalves, echinoids and crabs. These faunal elements, together with lithology and stratigraphy, provide information about palaeoecological and sedimentological condition of this area. © 2018 E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany.
Geologica Acta (16965728) 14(4)pp. 363-384
Upper Cretaceous mixed carbonate-siliciclastic sequences are among the most important targets for hydrocarbon exploration in the Moghan area, located in the eastern Para-Tethys Basin. Despite of their significance, little is known about their facies characteristics and depositional environments. Detailed facies analysis and paleoenvironmental reconstruction of these sequences have been carried out in eight surface sections. Accordingly, four siliciclastic facies, eight carbonate facies and one volcanic facies have been recognized. Detailed facies descriptions and interpretations, together with the results of facies frequency analysis, standard facies models and Upper Cretaceous depositional models of Para-Tethys Basin, have been integrated and a non-rimmed carbonate platform is presented. This platform was affected by siliciclastic influx, in the form of coastal fan delta and submarine fans in the shallow- to deep-marine parts, respectively. This model is interpreted to be shallower in the central and northeastern parts of the Moghan area. Toward the southeast and southwest, this shallow platform turns into deep marine settings along steep slopes without remarkable marginal barriers. © M. Omidvar, A. Safari, H. Vaziri-Moghaddam, H. Ghalavand, 2016 CC BY-SA.
Mohammadi, E. ,
Hasanzadeh-dastgerdi, M. ,
Ghaedi, M. ,
Dehghan, R. ,
Safari, A. ,
Vaziri moghaddam, H. ,
Baizidi, C. ,
Vaziri, M. ,
Sfidari, E. Carbonates and Evaporites (08912556) 28(3)pp. 321-345
The aim of this research is to shed light on the distribution of Rupelian (Early Oligocene) and evaporate deposits as evidences for timing and trending of opening and closure of the Tethyan Seaway. To accomplish these goals, four sets of data were scrutinized: (1) two stratigraphic sections (Ghohroud and Vidoja) of the Qom Formation in the southern and southwestern Kashan (to determine the age of their lower deposits), (2) results of the study of more than 100 stratigraphic sections of the Qom Formation, (3) Geological maps of Iran Sheets and (4) more than 30 geological maps of different parts of Iran. Consideration of four sets of data led to the following conclusions. Deposition of the Qom Formation (with Rupelian-Burdigalian range) took place in three NW-SE-trending basins: Sanandaj-Sirjan (fore-arc basin), Urumieh-Dokhtar magmatic arc (intra-arc basin) and Central Iran (back-arc basin). Marine conditions in the low latitudes of these three basins started in the Rupelian. Rupelian deposits are vastly distributed in the intra-arc and fore-arc basins but in the back-arc basin Rupelian deposits are deposited only in a few places in close proximity of the magmatic arc. It is remarkable that mostly all of the intra-arc Rupelian deposits-bearing sections are underlain by Eocene volcanic rocks. Latitudinally, the Rupelian deposits of the Qom Formatiom are deposited below 34 2′N, the Chattian deposits continue to 35 N, but above 35 N the Qom Formation is deposited during the Miocene, based on previous age dating; therefore, transgression of the Tethyan Seaway on the Iranian Plate started from the southeast and continued northwestward gradually. The last true Nummulites spp. became extinct at the top of Late Rupelian and all of the in situ Nummulites-bearing layers of the Qom Formation are Rupelian in age. According to the presence of Nummulites spp. (Nummulites fichteli, Nummulites vascus, Nummulites sp.), the lower 185 m of the Ghohroud section and whole deposits of the Vidoja section are attributed to the Rupelian. Evaporate deposits of the Qom Formation are deposited in a rather small area of Central Iran back-arc basin and are deposited totally in the Early Miocene (Aquitanian-Burdigalian). This indicates that due to the compressive tectonic regime in the Central Iran back-arc basin, the gates to the open ocean became restricted in the Early Miocene gradually. During the Aquitanain and Burdigalian, restricted marine conditions prevailed and episodic precipitation of evaporate deposits occurred. In the Qom area near the depocentre of the Qom basin, evaporates were precipitated episodically. Deposition of evaporate deposits took place along the concave side of an assumptive curved line crossing from SE of Anarak, Nain, Navab Anticline (SE of Kashan), Shourab (SE of Qom), immediate S, SW and W of Qom, N of Howz Soltan Lake, SW of Tehran, SW, W and SE of Varamin, NE of Garmsar and NW, N and NE of Semnan. Distribution of the Qom Formation, evaporate deposits and Rupelian deposits are illustrated on new maps shown herein as figures. © 2012 Springer-Verlag Berlin Heidelberg.
Carnets de Geologie (17652553) pp. 173-181
The limnic ostracode Frambocythere tumiensis zagrosensis subsp. nov. (Limnocytheridae, Timiriaseviinae), has been found for the first time in Iran. The strata containing this species are in the lower part of the Tarbur Formation in the interior Fars of the Zagros Mountains. The Late Maastrichtian age is indicated by rudists, larger foraminifers (Omphalocyclus macroporus, Loftusia spp.) and plank-tonic foraminifers(Contusotruncana contusa-Racemiguembelina fructicosa Zone) present in the upper part of the Tarbur Formation. The Maastrichtian age is confirmed by the occurrence in the same strata of the charophytes Platychara shanii, Peckichara cristellata and Stephanochara cf. producta. The genus Frambocythere COLIN, 1980, was until now known mostly from the Upper Maastrichtian to Middle Eoce-ne of southern Europe, India and China, as well as the Albian of the Democratic Republic of Congo. The presence of Frambocythere gr. tumiensis in Iran is therefore a newly recognized link between southern Europe and the Far East (China).
Revista Mexicana de Ciencias Geologicas (10268774) 28(3)pp. 555-565
A study of large benthic foraminifera from the 147 m-thick Qom Formation in the Chenar area (northwestern Kashan) is reported. One hundred and twelve thin sections were prepared and the distribution of benthic foraminifera was analyzed to reconstruct paleoenvironmental conditions. Study of these sections led to the identification of 28 genera and 38 species. On the basis of the recognized foraminifera, the section is comparable to Lepidocyclina- Operculina- Ditrupa Assemblage zone, and the age of the Qom Formation in the studied section is assigned to the Oligocene. Evidence of sea level changes is observed from bottom to top of the studied section. On the basis of large benthic foraminifera assemblages and microfacies features, three major depositional environments (inner shelf, middle shelf and outer shelf) were defined. The inner shelf facies is characterized by wackstone-packstone, dominated by miliolid and small perforate foraminifera. The middle shelf facies is represented by packstone-grainstone with diverse assemblage of large perforate benthic foraminifera. Outer shelf facies is dominated by large perforate benthic foraminifera as well as planktic foraminifera. The distribution of the Oligocene large benthic foraminifera in the studied area indicates that shallow marine carbonate sediments of the Qom Formation were deposited in a photic zone of tropical to subtropical environments. Finally, the correlation between the study area and some other sections of Central Iran indicates that sedimentation of the Qom Formation is continued from Late Rupelian to Chattian in northwest and Late Rupelian to Aquitanian in southeast direction.
Carbonates and Evaporites (08912556) 26(3)pp. 255-271
Qom Formation (Oligo-Miocene marine deposits, Central Iran) in the South of Kashan, was studied in order to determine its microfacies and depositional environment. Thirteen microfacies (MF A-M) were distinguished based on petrography, sedimentological features, components distribution and present fauna. According to recognized microfacies and absence of gravity deposits, real and continuous reef, barrier and storm structures, carbonate platform of the Qom Formation in South of Kashan developed on an open shelf without effective barriers separating it from the sea. The cooccurrences of miliolids and planktonic foraminifera in planktonic microfacies is the reliable evidences for absence of any reefal, oolitic and bioclastic barriers in depositional environment, and deposition of the study section on an open shelf, as in the absence of barrier, currents removed miliolids to deeper parts of sea (basin). Three major depositional environments were identified in the Oligo-Miocene succession in the study section, on the basis of the distribution of the foraminifera and vertical facies relationships. They include inner shelf, middle shelf and proximal outer shelf. Inner shelf includes MF A-G and characterized by abundant imperforate foraminifera. Middle shelf comprises MF H-J and characterized by association of larger benthic foraminifera with hyaline wall. Proximal outer shelf includes MF K-M and characterized by the presence of planktonic foraminifera and absence of larger benthic foraminifera, as well as abundance of lightindependent, heterotroph organisms. © Springer-Verlag 2011.
Carbonates and Evaporites (08912556) 20(2)pp. 131-137
An analysis of microfacies features and of larger benthic foraminiferal assemblages which include imperforate and perforate, was used to define microfacies types. The predominant microfacies are; 1) Rudist, orbitoidae wackestone packstone; 2) Rudist packstone; 3) Bioclast grainstone; 4) Orbitoidae, miliolids, bioclast wackestone packstone; 5) Dicyclina, miliolids, bioclast wackestone packstone; 6) Miliolids mudstone; 7) Peloidal, bioclast wackestone packstone; 8) Bioclast, ostracoda packstone grainstone. Three major depositional environments are identified in the Tarbur Formation on the basis of grain types, physical and biogenic sedimentary structures and vertical facies relationships. These include shallow subtidal (shelf lagoon), sand shoal and open marine. Tarbur Formation sediments were deposited on a ramp carbonate platform. Four depositional sequences were also recognized in the Tarbur Formation. TST sediments dominated by hyaline foraminifera and HST sediments dominated by various taxa of imperforate foraminifera. The assemblages of perforate and imperforate foraminifera and microfacies are used for interpretation of palaeoenvironment features of the Tarbur Formation.
